Conventionally, there is a technology of obtaining points which correspond among a plurality images acquired using two or more cameras (hereinafter referred to as corresponding points) and measuring a three-dimensional position of a subject from a positional relationship among the cameras and positions of the corresponding points on the respective images. This technology is utilized in various fields such as an in-vehicle advanced driver assistance system, a mobile device and a game machine. Particularly, a stereo camera system (hereinafter also referred to as a stereo camera) using two cameras is widely utilized.
For example, because a search range can be narrowed down in one dimension and corresponding points can be efficiently searched by the corresponding points being searched according to epipolar constraint conditions, in most stereo cameras, the corresponding points are searched according to the epipolar constraint conditions.
A rectification circuit parallelizes two images obtained with two cameras so that a point on one image exists on a search line such as an epipolar line on the other image. A parameter for parallelizing the two images is provided at the rectification circuit. This parameter is, for example, determined through calibration using an adjusting apparatus, or the like, upon manufacturing of the stereo camera.
However, there is a case where the parameter is displaced and becomes inappropriate due to temperature characteristics or vibration characteristics of a jig, or the like, of the adjusting apparatus, aging degradation of the stereo camera, or the like.
To modify such displacement, conventionally, characteristic points or characteristic regions on two images are calculated, and non-linear optimization processing, or the like, is performed using a corresponding point pair. There is a problem that it takes time to determine whether or not there is a parameter error for rectification, and, as a result, it takes time to perform processing of correcting the parameter error.